ACTIVITY SERIES
Introduction
Oxidation-reduction reactions, also known as redox reactions, comprise an extremely
important area of study in chemistry. These reactions provide energy in electrochemical
cells and have a veriety of commercial uses in batteries and solar cells. In addition,
oxidation-reduction reactions are involved in rusting, cleaning agents, photography, and
many other processes.
Redox reactions can be thought of as reactions in which electrons are exchanged
between one species that is oxidized and another that is recuded. Reduction involves the
gain of electrons, while oxidation involves the loss of electrons. A reduction reaction for
a metal ion can be written in the following manner:
*Diagram*
The oxidation reaction is written:
*Diagram*
*MR. STREIB: Fill in blank spots with correct characters*
____ is typically a metal with +n oxidation state, and n represents the number of
electrons (e-) gained. _____ is the metal in its reduced form.
An activity series of metals is a list that ranks metals accroding to their relative
activity. Metals at the top of the list are oxidized most readily to their metallic ion. They
tend to remain in ionic ____ form. Conversely, metals at the bottom of the list are
oxidized with difficulty. Their metallic ion is relatively active so they tend to be in the
reduced ____ form. In his investigation, you will establish any activity series based on
the ease with which metallic ions are reduced. The ions to be studied are Cu2+, Fe2+, H+,
Mg2+, Ag+, and Zn2+. The metals to be studied are Zn, Cu, Mg, and Fe.
Pre-Lab Discussion
Read the entire laboratory investigation and the relevant pages of your textbook. Then
answer the questions that follow.
1.
Define the terms oxidation and reduction. ________________________________
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2.
Are metallic ions the oxidized or reduced form of metals? Explain. ____________
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3.
What safety hazards are involved in this investigation and what precautions
should be followed? _________________________________________________
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4.
What will be the major information gained from this investigation? ___________
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5.
Write an example of a typical reduction half reaction for a metal ion. __________
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Problem
Can an activity series for metals be developed based on the reduction of certain ions in
solution?
Materials
chemical splash goggles
laboratory apron
latex gloves
well plate
marking pen
6 micropipets, filled with
the following solutions:
magnesium sulfate (MgSO4), 0.1 M
copper sulfate (CuSO4), 0.1 M
silver nitrate (AgNO3), 0.1 M
zinc sulfate (ZnSO4), 0.1 M
iron sulfate (FeSO4), 0.1 M
sulfuric acid (H2SO4), 3.0 M
steel wool
tweezers
zinc (Zn) strip
copper (Cu) strip
magnesium (Mg) strip
iron (Fe) strip
Safety
Wear your goggles and lab apron at all times during the investigation. Sulfuric acid is
extremely corrosive. Silver nitrate is toxic if ingested. It will cause stains to skin and
clothing. Wear gloves when handling silver nitrate or sulfuric acid. Wash any area of
contact with plenty of cold water.
Procedure
1.
Put on your goggles and lab apron. Set up and label the 24-well reaction
plate as shown in Figure 58-1. Place the well plate on a sheet of white
paper so you can more easily view the dark precipitates.
*Diagram*
Figure 58-1
2.
3.
4.
5.
Put on your latex gloves. Using the appropriate micropipet, place 20 drops
of 0.1 M zinc sulfate solution into the four wells in column 1. In a similar
fashion, place 20 drops each of 3.0 M sulfuric acid, iron sulfate, silver
nitrate, copper sulfate, and magnesium sulfate into the wells in columns 26 respectively. CAUTION: Sulfuric acid is extremely corrosive. Silver
nitrate is toxic if ingested. It will stain skin and clothing. Wear gloves
when handling these solutions. Wash any spills with plenty of cold water
and tell your teacher.
Using steel wool, clean strips of zinc, copper, magnesium, and iron. Place
the strips in wells A1-D1 as shown in Figure 58-1. Wait for two minutes
and check for a reaction. Record your observations in the Data Table.
Rinse and dry the strips.
In a similar fashion, repeat the process for columns 2-6. Continue to
record your observations in the Data Table.
Using a micropipet, dispose of the contents of the wells in column 4 in a
labeled container provided by your teacher. Rinse the rest of the solutions
down the drain. Clean up your work area and wash your hands before
leaving the laboratory.
Observations
DATA TABLE
1
ZnSO4
A
B
C
D
2
H2SO4
3
FeSO4
4
AgNO3
5
CuSO4
6
MgSO4
Zn
Cu
Mg
Fe
Critical Thinking: Analysis and Conclusions
1.
Which metal reacted with the largest number of solutions? (Interpreting data) ___
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2.
Which metal was the least reactive? (Interpreting data) _____________________
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3.
Which metal(s) reacted with sulfuric acid? (Interpreting data) _______________
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4.
Which metal ion reacted with all metals and what is the significance of these
results? (Drawing conclusions) ________________________________________
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5.
Rank the positive ions from the most easily recuded to least easily reduced and
write the reduction half reactions for each. (Making comparisons)
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Critical Thinking: Applications
1.
Magnesium blocks are often attached to iron storage tanks by a wire prior to
placing these tanks underground. What is the purpose of this? (Developing
hypotheses) ________________________________________________________
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2.
By convention, eight metals (ruthenium, rhodium, palladium, silver, osmium,
iridium, platinum, and gold) have been classified as “precious.” Would you
expect them to be easy or difficult to oxidize? (Making judgements) ___________
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3.
The element fluorine is one of the most reactive elements. Predict where it might
fit in the list in Analysis and Conculsions Question 5. (Hint: it reacts with metallic
silver to make silver fluoride.) (Making predictions) _______________________
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Going Further
1.
There are a number of “sacrificial” metals used to protect other metals. If
possible, contact boat, boat motor, and metal fabricators, find out how these
metals are utilized, then do a report on the topic.